View Full Version : engine firing frustrations
01-23-2005, 01:02:00 AM
okay i tried to fire my rebuilt small block for the 1st time today. and it would fire it just back fired through the carb. i think it might be either plug wires on wrong, dist not timmed quite right or i may have accidentally oout the dist in w/o no.1 at TDC. although i'm pretty sure i got that right.
anyone care to give some input?
01-23-2005, 01:24:00 AM
Eliminate one cause of the problem at a time. Check that all of the wires are going to the right place first off, easy to eliminate.
You can check that the distributor is in phase (ie not 180 degrees out) by having someone help you turn the engine over a few times. On the compression stroke if you have your finger over spark plug hole for #1 the air pressure will force it's way past your finger. At this point the distributor should point at approximately number 1.
01-23-2005, 01:44:00 AM
yeah that was half my problem today i was trying to get someone to help me. i even offerd to pay $20 !!!!! but none of my buddies wanted to help WTF man!! although maybe the blizzard like snow was a bit discouraging to sane people. i had to shovel off the car and the ground just to be able to put the new starter in. all they wouild have to of done was turn the key though.
oh well. i have a feeling, and am hoping, that it is just something as simple as plug wires. i did have to take then off a lot to put headers on and such. gonna check the easy stuff tomorrow it is supposed to be really cold.
01-23-2005, 11:35:00 AM
If it just "sneezes" out the intake every now and then you probably got it 180* off. Classic symptoms.
Spin the motor around until the balancer line is pointing at TDC. Pull the cap. Is it pointing at #1 plug wire? If so, it's not firing because it's 180* out. Yank it, drop it back in pointing at #6 plug wire and try again.
BTW- if the motor is up on TDC the rotor should already be a little PAST (clockwise from) the plug terminal. That assures you have a little bit of spark advance for easy first firing. Way better to have 22-26* of advance when first firing it up than to have -4*.
[This message has been edited by Damon (edited January 23, 2005).]
01-23-2005, 01:56:00 PM
Here's a good write up about dead timing an engine, it sounds like what you are after. http://www.nastyz28.com/ubb/biggrin.gif
01-23-2005, 10:38:00 PM
yepper thats what i have done..put the dist in 180 off. when i had the engine on the stand i WAS at TDC but i forgot that when i out the torque converter bolts in i had to spin the engine. DUUUHH. plus today i cranked it and had a timing light on and it didn't flash with the mark on the balancer. but i didn't mess with it much more than that becasue of the -5 wind chill!!! plus when i was trying to start it i found that the fuel bowl on my holley is leaking where the fuel fitting goes in becasue it is stripped out. so that sucks. i need to get a new bowl now and the only thing i could find in the summit or jegs catalogs were $65 chrome bowls which look dumb and are way more than i wanna spend just for a fuel bowl.
i have a 750 double pumper that i thought about just putting on so i could get it started and break in the cam. i don't know if it would work that well becasue it came off a 415 big block. anyone think it would atleast get the job done on a 311?(307)Just to break in the cam nothing more nothing less.
01-23-2005, 11:27:00 PM
The 750 dp should work fine regaurdless of what it came off of it may not be tuned just right for your car but the carb only lets a set amount of fuel through based on metered air flow, if it was another street motor chances are real good it will be fine, if it was a race only motor someone may have removed the front power valve and jetted it up you can look and see.
01-24-2005, 01:24:00 AM
naa the powwer valve is still there it was a street strip motor but mostly street. i kinda knew that it would atleast run with the bigger carb. i just figured that it would be rich. iono what jets are in it but i can almost gaurantee that they are oversized for my tame 307 compared to the 415. i guess the only problem i might have is that it might not want to run at low RPM's which when i break in the cam i won't be at low RPM's much anyway.
i'll prolly use the 750 if i can't come up with a new bowl by this weekend.
sweet thanks a bunch
01-28-2005, 02:26:00 PM
hay i had to set my timing with no help to. so this is what i did i pulled out the number 1 plug, i then taped up the end of 3/8,s socket ext. i put it in the number one hole and hit the key one click at a time untill the socket got kicked out .i then set the oil pump fitting to piont at number 5 spark plug wire i then set the rotor to just past numer 1 but not just 8 i dropped the distributor in . set your timing with a light some times like my distributor did not sit where it did in the past because the cam had some timing set in to it so now it sets as if its -6* . just my two cents eddie
01-29-2005, 05:16:00 PM
OOOKay so today i got the 750 carb swapped on and the timming issue worked out. i did infact put the dist in 180 out. so then i went to fire it. and the timing was off a little because it still sot a flame out the intake. however it ran. but that is my problem now. it onlt runns w/o dieing when the choke is on but when it does run it instatnlt goes up to about 3G's and keep climbing RPM. i tried startting it w/o the choke on but the engine revs up to about 1500 then dies. i tried adjusting the choke idle speed but i didn't help much. right now i think part of my problem is that i have straight headers on it. so tomorrow i'm going to put the mufflers on to gain some back pressure so maybe it will run below 1500 rpm.
so right now my theory is a mixture of minimal back pressure, timming that is off a little, and possibly the carb it not tunned to go on a basically stock 307 from a mild big block.
what do ya think?
01-31-2005, 12:49:00 AM
okay i know someone out there has a theory that either disagrees or agrees with mine
please shout them out
02-01-2005, 11:43:00 AM
hmm i have been thinking lately and it almost seems like a vacume leak. cuz maybe there is a leak somewhere and with the more fuek that the carb can put out the extra air is allowing it to run.
how hard would the engine have to back fire to bend the throttle plates? it did a couple of times. most of the time it was not real big but one time it made a big enough flame to see it through the snow covered plexigalss opening in the hood, where a scoop used to go through.
02-01-2005, 07:10:00 PM
How did you set the timing? I have found it a lot easier to start a motor with too much static timing, but not so easy to start one with not enough. If it fires but won't run you can try bumping the timing up a little and cracking open the idle screw a little. If everything else is OK this should get the motor running long enough to actually set the idle speed, and set the base timing with a timing light.
02-01-2005, 11:31:00 PM
man i feel like a dumbass
forgot that ome holley's have 2 big vacume ports on the throttle body.hhhmmm....
yeah i forgot to plug the back one which was like having the throttle plates crcked open becasue the carb was not jetted down adn there was oo much extra air going in